The present invention relates to reactive ion etching and more particularly to a system for preventing the propagation of plasma discharge down the gas feed path in such a system.
In the manufacture of semi-conductor integrated circuits, reactive ion etching (RIE) is coming into increased use for etching semi-conductor wafers to form thereon the patterns desired for circuit components. As the material being etched is typically in the form of a semi-conductor wafer which is thin and flat, it is desirable to energize the plasma by means of an electrode which is adjacent the wafer and through which the gas is introduced, e.g., through a series of openings in the electrode in the manner of a showerhead. To energize the plasma, a high voltage radio frequency (RF) signal is applied to the electrode. As the power levels used for etching have increased, one problem of which has developed is that the plasma discharge tends to propagate down the gas feed system. The gas feed system, including the usual gas pressure regulating system, is preferably grounded and thus potential gradients exists in the feed system which tend to generate plasma discharges just as they are created in the reactive ion etch chamber itself. Such propagation of the plasma discharge is undesirable, not only for the reason that it wastes RF power, but also in that the discharge can erode and damage the feed components and introduce contaminants into the process chamber. As is understood, the fabrication of integrated circuits demands exceptional purity and an avoidance of contaminants.
Among the several objects of the present invention, it may be noted the provision of a novel system for feeding gas to a reactive ion etch system; the provision of such a system in which propagation of the plasma discharge into the gas feed is eliminated, the provision of such a system which permits substantially unimpeded gas flow into the reaction chamber; the provision of such a system which facilitates the regulation of gas pressure by means outside the chamber; the provision of such a system which minimizes damage and contamination due to plasma discharges outside the reaction chamber; and the provision of such a system which is highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.